2. CQRS Races Sagas
Domain
Model

4. Get dataGet data
Change dataUser is looking at
stale data

5. Data correct as of
10 minutes ago
List of customers

6. List of customers
Customer Service Rep view
ID Name Phone
List of customers
Supervisor view
ID Name Phone Lifetime value

9. Queries
Commands
DB
Service
Layer
Input
Validation Validation
Rules
Queries
View Model
View Model
Updater
Publish
Client

11. Cancel OrderShip Order
Rules:
1. Cannot cancel shipped orders
2. Don’t ship cancelled orders

12. public class Order
{
public void Cancel()
{
if (status != OrderStatusEnum.Shipped)
//cancel
}
public void Ship()
{
if (status != OrderStatusEnum.Cancelled)
//ship
}
}

14. Looks like we’re stuck

15. The customer doesn’t want the products
No point in arguing

16. Rules:
1. Cannot cancel shipped orders
Because shipping costs money
That money would be lost if the customer cancelled
Because we refund the customers money
2. Don’t ship cancelled orders

27. www.NServiceBus.com

31. Queries
Commands
DB
Service
Layer
Input
Validation Validation
Rules
Queries
View Model
View Model
Updater
Publish
Client

32. CQRS Races Sagas
Domain
Model